Control of a surface condition of a wafer has recently attracted attention from the viewpoint of an increase in a yield in manufacturing of semiconductor devices. In a semiconductor device manufacturing process, films of various materials are formed on a silicon substrate. Therefore, an unnecessary film(s) or surface roughness is formed on a peripheral portion of the substrate. These days it is a common practice to transport a substrate while holding only a peripheral portion of the substrate with arms. With such a background, an unnecessary film, remaining on a peripheral portion of a substrate, may peel off during various processes and may adhere to a device formed on the substrate, resulting in reduced yield. Thus, in order to remove an unnecessary film from the peripheral portion of the substrate, a polishing apparatus is used to polish the peripheral portion of the substrate.
FIG. 45 is a schematic view of a conventional polishing apparatus. A polishing tape 205 for polishing a substrate W is pressed by a pressing member 208 against an edge portion of the substrate W. The pressing member 208 is coupled to an air cylinder 209, and a force that presses the polishing tape 205 against the substrate W is applied from the air cylinder 209 to the pressing member 208.
A peripheral portion of the substrate W is polished in the following manner. While the substrate W is being rotated about its axis, a liquid (e.g., pure water) is supplied onto an upper surface of the substrate W. The air cylinder 209 exerts a pressing force on the pressing member 208, which in turn presses the polishing tape 205 against the edge portion of the substrate W. The polishing tape 205 polishes the peripheral portion, including the edge portion, of the substrate W, thereby forming a stepped recess 210 as shown in FIG. 46 in the peripheral portion of the substrate W.
However, there are several problems in the conventional polishing apparatus. Specifically, a position of the polishing tape 205 is unstable at the beginning of polishing, and a polishing start position may be displaced from a predetermined position. Moreover, as shown in FIG. 47, the recess 210 may have a serrated inside surface, which can cause particles in a subsequent substrate processing.